Field monitoring and analysis of the early performance of unbonded concrete overlay using strain gauge readings

Spragues Road is a two-lane rural highway in the Regional Municipality of Waterloo, Ontario, Canada. The highway was reconstructed by using a 160 mm unbonded jointed plain concrete overlay over a 25 mm separation layer of high-stability hot-laid asphalt on the existing concrete base. Strain gauges were installed at the interface between the concrete and asphalt separation layer to study the behavior of the concrete. Five slabs were instrumented with concrete embedment strain gauges, placed longitudinally and transversely. Strain data have been collected every hour to monitor the strain values from January to August to explore the concrete overlay performance during winter, spring thaw, and summer seasons. This paper compares strain levels at various locations, namely: inner wheel-path, outer wheel-path, between wheel-path, at the centre of the slab, and close to the edge of the slab transversely or longitudinally. The differences of strain among various seasons are also discussed.